Deposition of antibodies to the collagen-like region of C1q in renal glomeruli of patients with proliferative lupus glomerulonephritis

Objective. To determine if antibodies to the collagen-like region of Clq (Clq-CLR) are present in the glomerular immune deposits of patients with systemic lupus erythematosus (SLE). Methods. Kidney tissues were obtained at autopsy, glomeruli were isolated, and glomerular basement membrane fragments were prepared, Antibodies were extracted with low pH or with DNase. Results. The concentrations of antibodies to Clq-CLR recovered from the glomeruli were greater than or equal to 50-fold higher per unit of IgG than that found in the serum or in the serum and interstitial fluid entrained in glomeruli, Antibodies to Clq-CLR were recovered from glomeruli of 4 of 5 patients with proliferative glomerulonephritis at autopsy. Conclusion. This is the first demonstration that antibodies to Clq-CLR are deposited and concentrated in the renal glomeruli of patients with SLE. These antibodies, thus, have the potential of contributing to the pathogenesis of lupus glomerulonephritis.